and conduct a new nuclear test, leaving no doubt leader kim jong-un isn't giving up his father's nuclear program. the u.s. might not is advanced warning of a new underground test. >> they have the capability, frankly, to conduct these tests in a way that make it very difficult to determine whether or not they are doing it. >> reporter: but there are signs they're ready to test if ordered. >> the north korean are maintaining a fairly high state of readiness at the test site. that means that if the order is given from pyongyang to go ahead, they can probably conduct the test in a few weeks. >> reporter: satellite imagery shows a tunnel entrance where the device may undergo final assembly. a bunker for personnel and equipment. and a communications network to make sure the order to detonate can be carried out. north korea's weapons-grade inventory is believed to include plutonium for up to 12 devices and enough enriched uranium for six more. how dangerous is all of this? >> i still think we're years away from north korea having a capability to deliver a nuclear war head on a missile even to